The present invention relates to a hand brake with an adjusting device for a motor vehicle including a two-part hand lever pivotably mounted on a support bracket fixedly secured to the vehicle body, and connected, by a pull member, to a wheel brake shoe, and a detent pawl supported on the hand lever and releasable with an actuation rod longitudinally displaceable in the hand lever shaft. The detent pawl cooperates with a toothed segment secured to the support bracket. The pull member is coupled to the hand lever by a spring-biased adjusting disc which is arranged concentrically with the hand lever and is movable relative to the hand lever upon release of the hand brake.
A hand brake with an adjusting device for a motor vehicle of the type described above is disclosed in European patent 162,749. In this hand brake, the pull member is connected to an adjusting member having a form of a disc segment supported on the support bracket for axial displacement and rotation about an axis which is concentric with the axis of rotation of the hand lever. The disc segment is biased in the circumferential direction with a torsion spring in such a manner that the pull member is held, under a certain spring load, free of backlash when the adjusting member is disconnected from the hand lever. In this hand brake, the hand lever is formlockingly connected with the adjusting member by an axially spring-biased coupling. The hand brake of EP-PS 162,749 is characterized by high costs of manufacturing and assembly. In addition, the functional reliability of the hand brake with such adjusting device strongly depends on the reliability of the coupling that connects the adjusting member and, thus, the pull member with the hand lever. An evident drawback of this known adjusting device is its requirement for a large mounting space in the vehicle because of axial displacement of the adjusting member.
EP-0 351 131 discloses an adjusting device that includes an adjusting disc which is supported concentrically with the hand lever but independently therefrom, is biased in the rotational direction by a helical spring, and is formed as a circumferentially toothed disc segment. This disc segment, upon brake application, is automatically coupled to the hand lever by an engaging dog supported on the disc segment and biased in a return direction with a return spring. The engaging dog is formed as a rocker one arm of which cooperates with the circumferential toothing of the disc segment and the other arm cooperates with a restoring stop element fixed on the support bracket in such a manner that, upon complete return of the hand lever to its release position, the hand lever is decoupled from the segment disc, and the disc segment is held in its position exclusively under the action of the segment disc-biasing spring.
A hand brake with an automatic adjusting device of the type described above places stringent requirements to the absence of backlash of the restoring stop associated with the engaging dog. This is because even relatively insignificant deflection of the engaging dog from a predetermined displacement can affect its cooperation with the restoring stop with the latter being positioned within acceptable tolerances, and, thus, the functional reliability of the adjusting device. Moreover, in the known construction of the adjusting device, for fixing the hand lever in its position corresponding to application of the brake, the arbitrary actuated detent pawl and the engaging dog of the adjusting member are mounted on the same bearing pin directly opposite each other, and, therefore, in particularly with an increased corrosion or clogging of the bearing elements, there is a danger of improper engagement of the detent pawl and the engaging dog, which further results in impairment of the functional reliability of the hand brake.
Accordingly, an object of the invention is an improved hand brake with an automatic adjusting device for a motor vehicle, which is characterized by reduced manufacturing costs and reduced requirement for a mounting space in the vehicle and which insures an optimal functional reliability of the adjusting device and, thus, the brake.